Initially, attention is directed to U.S. Pat. No. 4,227,419, granted Oct. 14, 1980, inventor: Kyong Park, title: "Capacitive Pressure Transducer," with the patent being assigned to the assignee of the present invention. As disclosed in the above-cited patent, capacitive pressure transducer systems may include a substantially fixed or slowly changing reference capacitor, and a variable capacitor including two closely spaced metal plates mounted in opposition to one another, with a sealed space between the conductive plates, and at least one of the plates mounted on a flexible diaphragm, so that as the pressure changes, the capacitance of this variable capacitor will change as the plates vary in their spacing. In the system as disclosed in the above patent, a bistable multivibrator, or flip-flop, is actuated in response to the charging first of the reference capacitor and secondly of the variable capacitor, with the time in each of the two states of the multi-vibrator being controlled by the time required for the charging of the reference capacitor and the variable capacitor, respectively. The square wave type output from the multi-vibrator is detected and integrated so that the output voltage increases as the capacitance of the variable capacitor increases, with increased pressure.
Incidentally, the linearity of these pressure transducer systems of the type shown in the above-cited patent is relatively good, but in the absence of compensation, a slight curvature or departure from linearity over a broad pressure range has been observed.
A principal object of the present invention is to improve the linearity, or the output voltage versus pressure characteristic of capacitive pressure transducer systems of the type discussed hereinabove.